Are you absolutley sure that roaming was on and working? I've not used a Smart SIM in roaming mode but I did have a Globe SIMs in roaming mode here in the UK.
If you had one of these SMART Plug & Talk thingies you can put your Smart SIM (not roaming) into it then activate Roaming on the SIM as you shut the device down, take the SIM out of the Plug and Talk then put it back into your phone, apart from that I don't know sorry.
Jim